This invention is in the field of food casings, in particular, edible casings made from collagen, and particularly such casings made for use with sausage.
While various types of collagen have been evaluated in the prior art for edible casing production, none have been successful in replacing the corium layer from bovine hides.
Thus U.S. Pat. No. 3,346,402 discloses the use of bovine tendon as a source of collagen, but has the deficiency that 5 to 20% gelatin must be added. The patent also states that treating tendon collagen with enzyme is not an alternative to adding gelatin because the collagen has inappropriate shrink characteristics when used in casing for fresh sausage.
U.S. Pat. No. 4,626,286 discloses the use of clean tendons to obtain collagen for manufacture of thin collagen film articles having superior mechanical properties. Cleaned tendons are ground and exposed to enzymes. Such a system of course has the disadvantage of requiring a specific tendon (bovine digital flexor) that is free of ligamentous tissue. This tendon is not available in sufficient quantity to meet the needs of sausage casing manufacture.
U.S. Pat. No. 4,407,829 discloses recovery of collagen from organs of the digestive system and other slaughter products of an animal, such as the lungs, udders etc. The patent does not disclose the use of connective tissue such as tendon, ligament and cartilage as suitable sources of collagen. While the patent mentions casings for food products as an objective, the example and claims do not disclose or recite manufacture of casing.
The current source of collagen for the preparation of food casings, such as sausage casings, is therefore the corium layer split from bovine hides. The market price for this material is generally tied to the price of the hides. Declining beef production coupled with increasing world demand for leather from hides has greatly increased the price for hides. Thus, there is a need for a lower cost source of collagen.
It is a purpose of this invention to develop a lower cost source of collagen for use in food casing compared to the corium layer from bovine hides.
It is a further purpose of this invention to provide a process for separating collagen from beef shanks and other animal parts which does not denature the collagen.
It is a further purpose of this invention to provide a method for preparing collagen casings by which the disadvantages of the prior art processes are avoided.
Still another purpose of this invention is to accomplish the forgoing purposes while providing an edible collagen casing.